Try driving 1/2 way across the country at max cruise, 89MPH, with a race exhaust and race suspension. You become quite atuned to how high the engine is reving as it drones on hour after hour...
STi in 6th is about 1000 RPM lower at freeway speeds.
If you want lower rolling resistance, go to 205 or 215s, not up to 235! BUT THAT WASN'T ON YOUR LIST...

Just going from 225 to 235 probably gives back any gains due to compound.